Grease a loaf tin with butter. If you have some, line with baking parchment. Nothing too fiddly, I just cut one long strip that goes down one side, across the bottom and up the other side.
Preheat the oven to 160C.
Cream your room temperature butter with your sugar until it's pale, light and fluffy.
Mix in the eggs, one at a time, beating really well after each egg. Don't worry if it starts to look a bit curdled, it'll all come good in a mo'.
Mix in your flour, cocoa and salt. If you've been using a mixer, do this bit by hand. It helps to keep the sponge light.
Stir in the chocolate chunks, the peanut butter and 30g of the salted peanuts. Just mix lightly, it's good to leave some chunks of peanut butter. You'll find them as a joyous surprise in the finished cake.
Spoon into a your tin, smooth out with the back of a spoon. Make a bit of a dip in the middle to account for rising. Sprinkle over the rest of your salted peanuts.
Bake for about 1 hour 15 minutes or until a skewer comes out clean.